Control circuit with two-position switch for latching circuit breaker



Feb 16, 1960 R. w. sTlNEMAN CONTROL CIRCUIT WITH Two-POSITION swITCH FCR LATCHING CIRCUIT BREAKER Flled May 14, 1956 United States PatentQie y z claims. (einem-+54) l This invention relates to improvements in control circuits for latching circuit'breakers', and 'more particularly concerns such a circuit incorporating manually operated switch means arranged to'cl'ose or tripthe circuit` breaker selectively and by its setting to indicate visually the condition of said circuit breaker. The invention isherein illustratively described by reference'h to the presently prel rwotrosirion t withcontactsflllfafterj the power contactortlllbgreaches The conV ctlv positions.`

ferred form thereof; however, will be recognized that certain modiicati'ons.andvv changes thereinjwith respect to details may be made without departing from the essential and characterizing features Vinvolved.VVV I,

In past practice the tripcoil of the latching circuit breaker was connected to be. energized either by closure of an automatic protection switch or by closure of the trip contact of a three-position neutral return switch of the manually operated type. Closure of the automatic protection switch energized a lock-out relay for the duration of `the fault to prevent premature energization of the close coil of the latching circuit breaker by manual closure of the close contact o fisaid three-position switch. With that arrangement it was usually considered" necessary to employ one or more indicator lights for providing a visual indication of the condition of the latching circuit breaker. In certain airplane installations having as many as nine or more latching circuit breakers a correspondingly large number of indicator lightsy was neces- 2,925,536 YPatented Feb, 16

alternately.Y Actuation of contacter 10g is eiectedV by a delayed sSequence mechanism in response to movement ofthe main power: contactor ltb between its openand closedf` positions. "This, delayed: sequence mechanism, comnionin 'such latching circuit breakers, isarrangedto' movefthegcontrol contacter v10gabruptly fromengagei ment withfconta'cts' 10f 'into engagement with contacts 10g' afterlthe power contactor Illfb` reaches open positiongand Y alternatively, togmove'the control-contacter ltlgk abruptlyL from; 'euggemetwithjcontacts' 10e' into 'engagement closed position, Thus thecontrol vcontactor is` actuated inramanner preventing continued energization of either theclbse-"coil 4i'ftllle'tri`p coil, and' theSe'coils. mayv be, designed 19t and 19g hold either or their two. given Late,ng-'circuitbreakers generally of thertype described andwithwhich the invention applies are used extensivelyin powertlsystemsand are provided for the purpose. of'-intelrrlllzitingl fand restoring power circuit .con-V nections fittunfvp,oints,outside,v thev circuit breakers Vthemselves;Y .Most commonly such circuitv breakers, are cone trailed by one VYor more automatic,protection, devices` and;V

one or more manually operated switches. In the present illustration the latchingl circuit breaker- 10: is Vsubject to sary, creating confusion and consuming considerable space on an indicator panel.

A general object of this invention is to provide an improved control circuit arrangement for a latching circuit breaker which avoids the need for separate indicators such as lights to represent the condition of the latching circuit breaker. More specifically, it is an object to provide such a control circuit performing all the functions of the previous circuits, but wherein a twoposition switch is employed in lieu of the former threeposition switch and which is so arranged that its setting may be observed visually and represents the existing condition of the latching circuit breaker.

With these and' other objects in View, the. invention resides in the novel' control circuit arrangement including the two-positionv switch means and related components connected thereto vas will be described hereinafter in connection with the accompanying.v drawing constituting a simplied schematic diagram of the control circuit.

Referring to the drawing, the latching circuit breaker 10 incorporates power contacts 10a interposed in the power conductor 12 interconnecting the load and the power source terminal 14. A power contactor 10b in the latching circuit breaker closes the power contacts 10a when the close coil 10c is energized. Opening of said power contacts is eiected by energization of the trip coil 10d. Control contacts 10e are connected in series with the energizing circuit for close coil 10c and similar contacts 10i are connected in series with the energizing circuit for the trip coil 10d. A contactor 10g is adapted to engage the two sets of control contacts 10e and 10i trips 4outfjtliey latching `r circuit breaker iu.

controlby a single protection device shown in the form ofan automatic overload protection device` 15.` Howeverg itA will beunderstood that the circuit breaker may. be.

controlled by. more than one automatic protection device andthat Vthe Vnature of these devicesY and theload orA fault conditions toV whichA they respond. may vary. Like! wise Athe illustrated arrangement7 includes but. oney manually. operated control. switch 13, and it-will be under-r stood that the circuit may be adapted to include` more thanj one such switch. Y v

The? illustrated protection device -16 includes an over-Y load sensing coil 16a which energizes the automatic pro,- tection switch actuator 16b to close the protection' switch 1 -6c yautomaticallyiin response to, but only during, ythe existence of an. overload condition in load circuit com' ductor. 12. The normally open contactseof switch 16C are interposed inI conductor 20 which extends from a D`.C.y voltage terminal 22 throughv a rectifier 24 to a conductor 26 connected'to" the Itrip coil 10d.V A conductor 28v connectsv the grounded coil 30a of lock-out relay 3Q to conductor 20. Trip coil 10d and lock-out relay coil 30a. are therefore energized whenever protection switchi Y116C vistolosed.'y Y

`Manually operated'two-position switch 18 has its cornmon terminal 18a connectedr to theVD-.C voltage terminal Z 2.-.'I`his switch has a trip contact 18h" and an alternativelyjenga'geable close contact 18C. The trip 'contact is connected. to conductor 26 hence to trip coil l0d,"so that positioning Yof switch 18 to close its 'trip contact The :close contact.A 18g is connectedto-Hthe common terminal o f y the; lock-,out relay.I This relay has aV normally Lclosedr contact 30'c'c'onnected'to the close coil through conductor 32. Thus positioning of switch 18 to engage its close contact 18a` causes energization of the close coil 10c if, and only if, the lock-out relay 30 is not then energized. Relay 30 also has a contact 30d which is connected to conductor 30 and which is closed by and during energization of relay coil 30a.

If, with manual switch 18 in the close position, the automatic protection switch 16a` closes, the lockout relay 30 transfers control of the latching circuit breaker from the manual switch 18 to Ythe trip circuit including switch 16e, rectier 24, trip coil 10d, contacts 10f and the D.C. voltage terminals. This circuit is held indenitefor a relatively,- lower, power dissipation rating. y

ly because contact 30d of relay 30 forms a holding circuit for the coil 30a of this relay when such coil is energized with switch 18 in its close position. If, after the emergency condition has expired, the operator Wishes to reclose the latching circuit breaker power contacts a, he simply moves the switch 18 momentarily to its position, which interrupts the holding circuit for the lockout relay, and then back to its close position, whereupon the close coil 10c becomes energized through contact 18e` of switch 18 and contact 30e of switch 30. Rectifier 24, being unidirectionally conductive, prevents ow of energizing current to coil 30a when switch 18 is moved into its trip position momentarily inthe reclose procedure.v

It will therefore be evident that if the manuallyoperated switch 18 is observed to be in the trip position the operator knows that the latching circuit breaker is tripped. Moreover, except in the event of an emergency, when the manually operated switch 18 is observed to bein its close position the operator knows that the latching circuit breaker is closed. If an emergency occurs to cause closure of protection switch 16C with the switch 18 in its close position, the operator will be apprised ofthe condition through observance of non-functioning of electrical loads and may resolve all ambiguityby a quick ip of switch 18 into and from its trip position to clear lock-out relay 30. The lock-out relay functions to prevent the operator from energizing the close coil 10c during persistence of an emergency condition which maintains protection switch 16C closed.

Thus it will be observed that the novel circuit arrangement accomplishes the foregoing and related objectives while performing all the control and protective functions of prior circuits, and that it accomplishes these results by the substitution of one type of switch for another and by the addition of one rectiier which may be a small silicon or other rectifier since it is required to carry current only for the brief interval required to trip the latching circuit breaker whereupon the contacts 10j become disengaged by contacter 10g. By this simple substitution and addition not only is indicator panel space saved, but an indicator light and its control relay are eliminated, as previously described.

I claim as my invention:

1. In combination with a latching circuit breaker having main power contacts, a close coil energizable to close said main power contacts, a trip coil energizable to open said main power contacts, control contact means operable with opening of said main power contacts to form an energizing connection for said close coil and further operable with closing of said main power contacts to form an energizing connection for said trip coil; a direct voltage source, automatic protection means including a normally open protection switch connected in series with said source and said trip coil, a unidirectionally conductive device interposed in the connections between said protection switch and said trip coil to permit energization of said coil from said source by closure of said protection switch, a manually operated twoposition switch having a common connection to the direct voltage source and having alternatively engageable trip and close contacts, a lock-out relay having a control coil connected to the interconnection between Y 4 the protection switch and said unidirectionally conductive device to be energized by closure of said protection switch, said lock-out relay having normally closed contacts opened by energization of said relay coil and connected between said close coil and the close contact of said two-position switch,.saidrelay further having normally open holding contacts' closed by energizatrion `of said-`relay coil and connected between said relay coil and the close contact of said two-position switchto form a holding circuit for said relay uponlenergization of said relay coilrwith said manually operated switch inthe position to engage its close contact, and means connecting the trip contact of said two-positionswitch to said trip coil to form an energizing circuit for said trip`coil-through said energizing connection therefor byclosure of said trip contact of said Atwo-position switch, positioning of said two-position switch to engage its VVclose contact with said relaypcoil deenergized `forminrgnan energizinglcircuit for said ,close coil through the energizingconnection therefor, whereby the position. yofsaid two-position switch normally indicates Vthe condition of said latching circuit breaker. Y j

2. In combination with a latching circuit breakerhaving main power contacts, a close coil venergizable to close said main power contacts, `a trip coil energizable to open said main power contacts,4 control contact 4means operable with opening ofrsaidma'in power contacts to form an energizing connection Yfor said close coil and further operable with closing of Vsaid main power contacts to form an energizing connection for said trip coil; a direct voltage source, two-position switch means connected for applying source voltage to said trip coil in one position of said two-position switch means and for applying source voltage to said close coil in the other position of said two-position switch means, a rectifier, and a protection switch connected between said trip coil and said direct voltage source, said rectifier being connected between said trip coil and said protection switch, with the latter arranged to be actuated for applying source voltage to said trip coil, through said rectifier, and relay means connected to the interconnection between said rectiier and said protection 'switch for energization by actuation of said protection switch, said relay means having a normally closed contact opened by energization of such relay means and connected, when opened, to interrupt the application of source voltage by said two-position switch means to said close coil, said relay means also having a normally open contact closed by energization of such relay means and connected, when closed, to apply source voltage to said relay means through the two-position switch means in said other position thereof. i

References Cited in the le of this patent UNITED STATES PATENTS 1,863,627 Gray June 21, 1932 1,885,157 Traver E Nov. 1, 1932 2,550,496 Reifschneider Apr. 24, 1951 FOREIGN PATENTS 453,801 France June 17, 1913 524,403 France Sept. 3, 1921 

